Microbeam AMS for Trace Element and Isotopic Studies

A microbeam Accelerator Mass Spectrometry (AMS) system has been developed at the CSIRO Heavy Ion Analytical Facility (HIAF) in Sydney, known as AUSTRALIS: A.M.S. for Ultra Sensitive TRAce eLement and Isotopic Studies. Based on a 3MV Tandetron, the system is designed for in-situ micro analysis of geological samples by mass spectrometric method virtually unrestricted by molecular and isobaric interferences. The microbeam source was developed from a HICONEX source, producing a 30 μm diameter Cs+ beam routinely, but designed to operate ultimately at resolution as high as 1 μm. The source features a high magnification sample viewing system in the reflected geometry, facilitating sample positioning and tuning of the primary beam. Isotope systems measured routinely at present include Pb and S isotopes, conducted at 1.5 to 2 MV terminal voltage. Lead isotopes are measured as Pb4+ ions, from either Pb−, PbO− or PbS− injected ions. Sulfur isotopes are measured as S2+ or S3+ ions from injected S− ions. A fast bounci...